1. Field of the Invention
This invention relates to cabinet constructions and in particular to refrigeration appliance cabinet constructions having plastic liners and foamed-in-place insulation.
2. Description of the Prior Art
In one conventional refrigeration appliance cabinet construction, a plastic liner is inserted in spaced relationship to an outer metal cabinet shell and insulation is foamed-in-place therebetween. Conventionally, the insulation comprises polyurethane material which tends to bond strongly to the outer surface of the plastic liner.
It has been found that in conventional use of such refrigeration appliances, thermal expansion and contraction occurs as a result of variations in the ambient and refrigerated temperatures. Cracking of the liner has, at times, resulted because of the differential thermal expansion characteristics of the cabinet materials. One improved form of such a refrigeration appliance cabinet construction utilizes selected foam release means at different stress points in the cabinet construction to permit movement between the foam and plastic liner materials thereat to prevent such cracking.
In another form of improved refrigeration appliance cabinet construction, the entire outer surface of the liner is provided with a foam release laminate. The laminate is formed of deformable material so that it may be adhered to the plastic material prior to the thermoforming of the plastic material into the liner configuration. Thus, this improved liner construction provides a low cost arrangement effectively eliminating the cracking problem while yet permitting the use of conventional liner plastic materials and foam insulation materials.
It has been found, however, that some adhesion between the foam insulation and the liner is desirable in selected areas in providing improved structural integrity and rigidity to the liner and cabinet construction.
In one form of refrigerator cabinet construction, as shown in U.S. Pat. No. 3,078,033 of Keith K. Kesling, a thin sheet of material is applied over the formed liner to prevent adhesion of the polyurethane foam thereto. Colin S. Hocking et al. U.S. Pat. No. 3,150,796 shows a similar sheet, which is removable from the liner to which the foamed insulation adheres. In Keith K. Kesling U.S. Pat. No. 3,294,662, a refrigerating apparatus is shown utilizing a parting agent on the surfaces of the liner adjacent selected portions thereof to prevent adhesion of the foam insulation to the liner thereat.
In Paul E. Kronenberger U.S. Pat. No. 3,719,303, a foam release agent is applied to the inner surface of the cabinet shell to accommodate the thermal expansion coefficient differentials.